SMEFT effects on gravitational wave spectrum from electroweak phase transition

Future gravitational wave observations are potentially sensitive to new physics corrections to the Higgs potential once the first-order electroweak phase transition arises. We study the SMEFT dimension-six operator effects on the Higgs potential, where three types of effects are taken into account: (i) SMEFT tree level effect on $\varphi^6$ operator, (ii) SMEFT tree level effect on the wave function renormalization of the Higgs field, and (iii) SMEFT top-quark one-loop level effect. The sensitivity of future gravitational wave observations to these effects is numerically calculated by performing a Fisher matrix analysis. We find that the future gravitational wave observations can be sensitive to (ii) and (iii) once the first-order electroweak phase transition arises from (i). The dimension-eight $\varphi^8$ operator effects on the first-order electroweak phase transition are also discussed. The sensitivities of the future gravitational wave observations are also compared with those of future collider experiments.Comment: 32 pages, 16 figures; section 6 was added for more explanation

Quantum Resonance viewed as Weak Measurement

Quantum resonance, i.e., amplification in transition probability available under certain conditions, offers a powerful means for determining fundamental quantities in physics, including the time duration of the second adopted in the SI units and neutron's electric dipole moment which is directly linked to CP violation. We revisit two of the typical examples, the Rabi resonance and the Ramsey resonance, and show that both of these represent the weak value amplification and that near the resonance points they share exactly the same behavior of transition probabilities except for the measurement strength whose difference leads to the known advantage of the Ramsey resonance in the sensitivity. Conversely, this suggests that the weak value may be measured, for instance, through the Ramsey resonance. In fact, we argue that previous measurements of neutron electric dipole moment have potentially determined the imaginary component of the weak value of the spin of neutrons with higher precision than the conventional weak value measurement via neutron beams by three orders of magnitude.Comment: 13 pages, 2 figure

Gluino-mediated electroweak penguin with flavor-violating trilinear couplings

In light of a discrepancy of the direct $CP$ violation in $K\to\pi\pi$ decays, $\varepsilon'/\varepsilon_K$, we investigate gluino contributions to the electroweak penguin, where flavor violations are induced by squark trilinear couplings. Top-Yukawa contributions to $\Delta S = 2$ observables are taken into account, and vacuum stability conditions are evaluated in detail. It is found that this scenario can explain the discrepancy of $\varepsilon'/\varepsilon_K$ for the squark mass smaller than 5.6 TeV. We also show that the gluino contributions can amplify $\mathcal{B}(K \to \pi \nu \overline{\nu})$, $\mathcal{B}(K_S \to \mu^+ \mu^-)_{\rm eff}$ and $\Delta A_{\rm CP}(b\to s\gamma)$. Such large effects could be measured in future experiments.Comment: 30 pages, 8 figures; references added, version published in JHE

New physics searches at the ILC positron and electron beam dumps

We study capability of the ILC beam dump experiment to search for new physics, comparing the performance of the electron and positron beam dumps. The dark photon, axion-like particles, and light scalar bosons are considered as new physics scenarios, where all the important production mechanisms are included: electron-positron pair-annihilation, Primakoff process, and bremsstrahlung productions. We find that the ILC beam dump experiment has higher sensitivity than past beam dump experiments, with the positron beam dump having slightly better performance for new physics particles which are produced by the electron-positron pair-annihilation.Comment: 26 pages, 7 figure